interaction btn apache and cronolog

Can you recommend where I can read about the interaction btn
apache
and cronolog? I have a problem in an apache server setup
where the
output (created through cronolog) is corrupt. It sure looks
like 2
processes were writing to the same file and one process
overwrote the
other one.

So I have lines in the output logs like this:

CSID=L0CSID=C05504

Here, it looks like a line starting CSID=L08956 got
overwritten right
after the "0" character and the other process
started writing
"CSID=C05504" to where the file ptr was.

Not knowing the interaction btn cronolog and apache, it is
hard for me
to debug this.

I'm on apache 2.0.54, cronolog 1.6.2

Thanks

Thushara

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Thushara Wijeratna wrote:
> Can you recommend where I can read about the
interaction btn apache
> and cronolog? I have a problem in an apache server
setup where the
> output (created through cronolog) is corrupt. It sure
looks like 2
> processes were writing to the same file and one process
overwrote the
> other one.
> 
> So I have lines in the output logs like this:
> 
> CSID=L0CSID=C05504
> 
> Here, it looks like a line starting CSID=L08956 got
overwritten right
> after the "0" character and the other process
started writing
> "CSID=C05504" to where the file ptr was.
> 
> Not knowing the interaction btn cronolog and apache, it
is hard for me
> to debug this.
> 
> I'm on apache 2.0.54, cronolog 1.6.2

This may happen if two virtual hosts are piping logs trough
cronolog
and cronolog logs into the same file.

Basically apache just opens the log program and writes
requests to it
no synchronization takes place. Make sure every cronolog
instance writes
to it's own file.

-- 
Georgi Chorbadzhiyski
http://georgi.unixsol.org/


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Thanks Georgi, in my case there is only one virtual host,
but of
course there are around 500 httpd child processes running
and writing
into one cronolog.

That is the part that I couldn't quite grasp. When I do a ps
auxww, I
see a cronolog process (just 1) all the time, so it sure
looks like
all the httpd children are writing to this one cronolog
process.

Tp avoid corruption, should we have one cronolog process for
each
httpd child, instead?

Thushara

On 10/11/06, Georgi Chorbadzhiyski <gfunixsol.org> wrote:
> Thushara Wijeratna wrote:
> > Can you recommend where I can read about the
interaction btn apache
> > and cronolog? I have a problem in an apache server
setup where the
> > output (created through cronolog) is corrupt. It
sure looks like 2
> > processes were writing to the same file and one
process overwrote the
> > other one.
> >
> > So I have lines in the output logs like this:
> >
> > CSID=L0CSID=C05504
> >
> > Here, it looks like a line starting CSID=L08956
got overwritten right
> > after the "0" character and the other
process started writing
> > "CSID=C05504" to where the file ptr was.
> >
> > Not knowing the interaction btn cronolog and
apache, it is hard for me
> > to debug this.
> >
> > I'm on apache 2.0.54, cronolog 1.6.2
>
> This may happen if two virtual hosts are piping logs
trough cronolog
> and cronolog logs into the same file.
>
> Basically apache just opens the log program and writes
requests to it
> no synchronization takes place. Make sure every
cronolog instance writes
> to it's own file.
>
> --
> Georgi Chorbadzhiyski
> http://georgi.unixsol.org/

>
>
------------------------------------------------------------
---------
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HTTP Server Project.
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>
>

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Thushara Wijeratna wrote:
> Thanks Georgi, in my case there is only one virtual
host, but of
> course there are around 500 httpd child processes
running and writing
> into one cronolog.
> 
> That is the part that I couldn't quite grasp. When I do
a ps auxww, I
> see a cronolog process (just 1) all the time, so it
sure looks like
> all the httpd children are writing to this one cronolog
process.
> 
> Tp avoid corruption, should we have one cronolog
process for each
> httpd child, instead?

Oh no, that would be overkill and I don't think it is even
possible to
make such configuration. May be there is some bug in
cronolog. I've
used cronolog on some pretty heave loaded sites and never
saw such a
problem like yours.

Can you try rotatelogs program from apache distribution and
see if the
problem persists.

-- 
Georgi Chorbadzhiyski
http://georgi.unixsol.org/


------------------------------------------------------------
---------
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Server Project.
See <URL:http://htt
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Hi Georgi,

Thanks for that info. Digging into this a bit more, I find
we're using
a modified cronolog - sorry I didn't see this before. The
one big
difference seems to be that we're using getc, vs read call
to read the
input in our cronolog.c. I'm suspecting that buffer size
mismatch has
something to do with this (getc would buffer with 8192 and
the
original cronolog seems to buffer 65536 bytes)

Apache writes from multiple child processes cannot be
interleaved
right? Even if we used getc instead of read, shouldn't we
still get
the bytes in the order apache processes wrote them?

Thanks,
Thushara


On 10/11/06, Georgi Chorbadzhiyski <gfunixsol.org> wrote:
> Thushara Wijeratna wrote:
> > Thanks Georgi, in my case there is only one
virtual host, but of
> > course there are around 500 httpd child processes
running and writing
> > into one cronolog.
> >
> > That is the part that I couldn't quite grasp. When
I do a ps auxww, I
> > see a cronolog process (just 1) all the time, so
it sure looks like
> > all the httpd children are writing to this one
cronolog process.
> >
> > Tp avoid corruption, should we have one cronolog
process for each
> > httpd child, instead?
>
> Oh no, that would be overkill and I don't think it is
even possible to
> make such configuration. May be there is some bug in
cronolog. I've
> used cronolog on some pretty heave loaded sites and
never saw such a
> problem like yours.
>
> Can you try rotatelogs program from apache distribution
and see if the
> problem persists.
>
> --
> Georgi Chorbadzhiyski
> http://georgi.unixsol.org/

>
>
------------------------------------------------------------
---------
> The official User-To-User support forum of the Apache
HTTP Server Project.
> See <URL:http://htt
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>    "   from the digest:
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>
>

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Seems like the parent apache process creates the pipe to
cronolog. The
children must be sending their output to the parent that
will in turn
pipe it to cronolog.

The only other thing is that we're using an environment
variable
expansion (macro) in the CustomLog string, as described here
:

http://www.st
anford.edu/dept/itss/docs/oracle/10g/server.101/q20201/mod/m
od_log_config.html#formats

Any clues as to how I can further debug this is much
appreciated.

Thushara

On 10/20/06, Thushara Wijeratna <thushwgmail.com> wrote:
> Hi Georgi,
>
> Thanks for that info. Digging into this a bit more, I
find we're using
> a modified cronolog - sorry I didn't see this before.
The one big
> difference seems to be that we're using getc, vs read
call to read the
> input in our cronolog.c. I'm suspecting that buffer
size mismatch has
> something to do with this (getc would buffer with 8192
and the
> original cronolog seems to buffer 65536 bytes)
>
> Apache writes from multiple child processes cannot be
interleaved
> right? Even if we used getc instead of read, shouldn't
we still get
> the bytes in the order apache processes wrote them?
>
> Thanks,
> Thushara
>
>
> On 10/11/06, Georgi Chorbadzhiyski <gfunixsol.org> wrote:
> > Thushara Wijeratna wrote:
> > > Thanks Georgi, in my case there is only one
virtual host, but of
> > > course there are around 500 httpd child
processes running and writing
> > > into one cronolog.
> > >
> > > That is the part that I couldn't quite grasp.
When I do a ps auxww, I
> > > see a cronolog process (just 1) all the time,
so it sure looks like
> > > all the httpd children are writing to this
one cronolog process.
> > >
> > > Tp avoid corruption, should we have one
cronolog process for each
> > > httpd child, instead?
> >
> > Oh no, that would be overkill and I don't think it
is even possible to
> > make such configuration. May be there is some bug
in cronolog. I've
> > used cronolog on some pretty heave loaded sites
and never saw such a
> > problem like yours.
> >
> > Can you try rotatelogs program from apache
distribution and see if the
> > problem persists.
> >
> > --
> > Georgi Chorbadzhiyski
> > http://georgi.unixsol.org/

> >
> >
------------------------------------------------------------
---------
> > The official User-To-User support forum of the
Apache HTTP Server Project.
> > See <URL:http://htt
pd.apache.org/userslist.html> for more info.
> > To unsubscribe, e-mail: users-unsubscribehttpd.apache.org
> >    "   from the digest:
users-digest-unsubscribehttpd.apache.org
> > For additional commands, e-mail: users-helphttpd.apache.org
> >
> >
>

------------------------------------------------------------
---------
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Server Project.
See <URL:http://htt
pd.apache.org/userslist.html> for more info.
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   "   from the digest: users-digest-unsubscribehttpd.apache.org
For additional commands, e-mail: users-helphttpd.apache.org

Seems like the parent apache process creates the pipe to
cronolog. The
children must be sending their output to the parent that
will in turn
pipe it to cronolog.

The only other thing is that we're using an environment
variable
expansion (macro) in the CustomLog string, as described here
:

http://www.st
anford.edu/dept/itss/docs/oracle/10g/server.101/q20201/mod/m
od_log_config.html#formats

Any clues as to how I can further debug this is much
appreciated.

Thushara

On 10/20/06, Thushara Wijeratna <thushwgmail.com> wrote:
> Hi Georgi,
>
> Thanks for that info. Digging into this a bit more, I
find we're using
> a modified cronolog - sorry I didn't see this before.
The one big
> difference seems to be that we're using getc, vs read
call to read the
> input in our cronolog.c. I'm suspecting that buffer
size mismatch has
> something to do with this (getc would buffer with 8192
and the
> original cronolog seems to buffer 65536 bytes)
>
> Apache writes from multiple child processes cannot be
interleaved
> right? Even if we used getc instead of read, shouldn't
we still get
> the bytes in the order apache processes wrote them?
>
> Thanks,
> Thushara
>
>
> On 10/11/06, Georgi Chorbadzhiyski <gfunixsol.org> wrote:
> > Thushara Wijeratna wrote:
> > > Thanks Georgi, in my case there is only one
virtual host, but of
> > > course there are around 500 httpd child
processes running and writing
> > > into one cronolog.
> > >
> > > That is the part that I couldn't quite grasp.
When I do a ps auxww, I
> > > see a cronolog process (just 1) all the time,
so it sure looks like
> > > all the httpd children are writing to this
one cronolog process.
> > >
> > > Tp avoid corruption, should we have one
cronolog process for each
> > > httpd child, instead?
> >
> > Oh no, that would be overkill and I don't think it
is even possible to
> > make such configuration. May be there is some bug
in cronolog. I've
> > used cronolog on some pretty heave loaded sites
and never saw such a
> > problem like yours.
> >
> > Can you try rotatelogs program from apache
distribution and see if the
> > problem persists.
> >
> > --
> > Georgi Chorbadzhiyski
> > http://georgi.unixsol.org/

> >
> >
------------------------------------------------------------
---------
> > The official User-To-User support forum of the
Apache HTTP Server Project.
> > See <URL:http://htt
pd.apache.org/userslist.html> for more info.
> > To unsubscribe, e-mail: users-unsubscribehttpd.apache.org
> >    "   from the digest:
users-digest-unsubscribehttpd.apache.org
> > For additional commands, e-mail: users-helphttpd.apache.org
> >
> >
>

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